The legalization of marijuana in Colorado and Washington in 2012 is the most dramatic change in substance abuse policy in the United States since the end of Prohibition. These states are implementing regulatory and enforcement systems for the retail sales of recreational marijuana to adults 21 years or older, akin to state controls on the sale of alcohol. In 2013, the U.S. Department of Justice (DOJ) issued directives that it would monitor whether these states implemented strong and effective regulatory and enforcement systems that among other DOJ priorities, prevented distribution of marijuana to youth. A retail sales intervention that has been effective at reducing illegal alcohol sales to minors (and intoxicated patrons) is alcoholic beverage server training (or Responsible Beverage Service training - RBS), which is currently required or incentivized by 36 states. Colorado recently enacted a law for incentivized marijuana vendor training (RMV) for retail licensees and employees and Washington is considering RMV. In this Phase I SBIR, we will evaluate the feasibility of creating and evaluating an online RMV by achieving the following aims: 1) to explore the concept/content of RMV with a) owners/managers and clerks in retail outlets and b) state and local regulators and enforcement officials; 2) to examine potential under-age sales with owners/managers, clerks, and minors who use marijuana; 3) to develop a prototype RMV in flowcharts and storyboards and by programming one module; 4) to evaluate the prototype RMV with owners/managers, clerks, and local regulators/officials; 5) to identify licensed marijuana retail outlets eligible for inclusion in a randomized trial in Phase II; and 6) to estimate current refusal rates of sales of marijuana to minors using pseudo-patron assessment. An Expert Advisory Board comprised of local and state regulators, retail cannabis licensed sellers, and experts in responsible beverage service training will advise on research procedures and evaluate study outcomes for feasibility of moving to full production and evaluation of the RMV in Phase II research. The long-term objectives of the SBIR research are urgently needed and extremely significant as increased drug availability is linked to marijuana initiation and many minors drink alcohol despite similar state controls. Also, the proposed research will have a very large impact, for it will create a model of effective RMV by a third-party (not the cannabis industry) that can be used by states that have legalized retail marijuana sales or will do so in th future. The online RMV program will be a first-of-its-kind intervention for a highly unique circumstance, the first legal U.S. retail markets for marijuana. The commercial potential for RMV by a third party outside the cannabis industry is currently untapped, and the retail cannabis market is poised to grow tremendously in the next few years. Staff at the National Institute on Drug Abuse (NIDA) has confirmed that research on RMV, with its goal of preventing distribution to minors, fits NIDA's priority to support research on social, behavioral, and public health impacts of policy changes on marijuana, including recreational marijuana legalization.